DE2558491B2 - VOLUME SPEAKERS - Google Patents

Description

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The invention relates to an electroacoustic ^; cal device, especially a ribbon speaker.

The invention can be applied to electroacoustic band transducers, especially ribbon speakers. The latter are used in the Consumer electronics, cinema technology, sound reinforcement in concert halls and in other cases in where a high quality sound is required.

There are ribbon speakers (CS-PS 1 17 767, US-PS 35 64 163) known that contain permanent magnets, in which a sound reproduction ribbon is arranged in the working air gap between the poles, the thickness of which is constant in the transverse direction

The magnetic induction in the air gap between the permanent magnets increases towards the center of the Working air gap, although it maintains high values in the vicinity of the pole, decreases quickly. On the edges of the audio playback ribbon a greater electromagnetic force acts compared to the central part. This leads to, that no high degree of phase equality of the vibrations of all points of the sound reproduction ribbon as a result of the creation of traveling waves in the direction of the width of the audio playback ribbon is guaranteed. A relatively high oscillation amplitude of the edges of the sound reproduction ribbon has in Combination with a disturbance of the phase equality results in various sound distortions. About that in addition, the middle part of the audio playback ribbon actually puts a strain on his in this case Edges, which is also a source of sound distortion. After all, mainly the If edges vibrate, the audio playback ribbon is constantly exposed to bending stresses in the transverse direction and can fail quickly.

The one known ribbon speaker (US-PS 35 64 163) has a sound playback ribbon variable Thickness in the longitudinal direction for sound reproduction, that in the direction from the central part to the edges, i.e. towards the Attachment points of the sound reproduction ribbon on the frame increases by the formation of standing waves in the

20 mi? Permanent magnets and TidgabeBändchen, each of which m, work.

S JSÄ1Ä ^Z S ° ÄTS £ TE

Ribbon edges near the pole

SS

Working air gap between the poles of the permanent magnets

25 The Bändcneniauispn *; .. *. contains (see. Fig. 1) a _w sound reproduction ribbon 1, which, in the cross-section darge-SlUm working air gap between the poles wound S of permanent magnets 2 The poles of permanent magnets 2 are in a zur_ audio frequency current in T ⁰ ™ ¹ ? ^ ⁸ ^ « _{Strength of} the« vertical projection shown The strength of the ^ SSEta ^ lUclMm. 1 grows in the direction of the poles NundS to its center hm.

Figure 2 is a graph showing the change of the magnetic induction Bim working air gap zTifchen the 'poles N and 5 of the permanent magnets 2. The electrical conductivity of Tonw.edergabe-BandchensTin direction of its width varies so that BETM passage of Tonfrequenzstromes by the sound ribbon 1 the condition:

Bi = const

Ä-'nignetic induction on an arbitrary selected longitudinal generating line of the sound reproduction ribbon 1

ι = audio frequency current on the same line. According to this condition, the values are the electromagnetic force in a correcting point of the sound reproduction ribbon 1 at any point in time

55 same.

1 sheet of drawings

Claims (1)

Claim: Ribbon loudspeaker with permanent magnets forming a magnet system and with audio playback ribbons, each of which lies in the working air gap between the poles of the associated permanent magnets, characterized in that the thickness of the electrically conductive layer of the audio reproduction ribbon (1) in the direction from the ribbon edges near the pole of the permanent magnets (3) to the ribbon center increases lift!"